In many applications of bottles and other containers, it is important that a closure provide a good seal with the container so that the contents of the container do not leak out or are not exposed to contaminants from the environment external to the container. Providing a consistent seal on injection molded containers can be particularly challenging because of the likelihood of small defects on the inside wall of the container neck, created by a scratch in the tooling, by the capping operation, or by some other cause.
Numerous closures are known to incorporate a plug seal depending downardly from a top ring or cap, the plug seal being in intimate contact with the inner neck wall of the container and having a bead or raised annular ridge on the external wall thereof, the beads being used to enhance the seal and/or to increase friction to prevent the closure from being forced off the container by internal pressure. Several prior art designs incorporate two or more beads. See, for example, see U.S. Pat. No. 2,894,654 (Lohrer); U.S. Pat. No. 3,001,659 (Schultz); U.S. Pat. No. 3,032,226 (Terwilliger); U.S. Pat. No. 3,057,503 (Salzmann); U.S. Pat. No. 3,109,547 (Wood); U.S. Pat. No. 3,109,548 (Wood); U.S. Pat. No. 3,473,685 (Karlan); U.S. Pat. No. 3,540,612 (Brady); U.S. Pat. No. 3,693,847 (Gibson); U.S. Pat. No. 3,924,771 (Cleff); U.S. Pat. No. 3,944,104 (Watson); U.S. Pat. No. 4,279,353 (Honma); U.S. Pat. No. 4,342,400 (Llera); and U.S. Pat. No. 4,380,304 (Anderson).
However, the prior art closures suffer from several deficiencies. Some existing closures space the multiple beads closely together, prohibiting each from moving independently of the other(s) to accommodate variations in the container neck wall. Additionally, in some closures, the wall of the plug seal is sufficiently thick along its entire length to impede the independent movement of individual sealing beads. Yet further, the plug seal of some existing closures is enclosed or capped at its distal end, significantly impairing the ability of the plug seal walls and beads to flex to match the container neck wall.
Another deficiency is that the plug seals of many existing closures have thin walls relative to their length, making them difficult to injection mold with consistency. In addition, uniformly thin walls may provide insufficient stiffness where the plug seal attaches to the top ring or cap of a closure. Further, many existing closures have equal sized beads so that if the plug seal wall is able to flex along its length, one or more of the beads may be deformed sufficiently to be no longer in contact with the neck wall around its entire periphery.